Burner ignition system

ABSTRACT

A burner ignition system for connection to a source of alternating current electric energy. The system has a spark generator, including an ignition transformer. The primary of ignition transformer is connected to a controlled rectifier. The trigger circuit for the controlled rectifier includes a series arrangement of a rectifier, a capacitance and a voltage breakdown device.

United States Patent 1 Budlane [4 1 Jan. 9, 1973 s41 BURNER IGNITIONSYSTEM 3,529,910 9/1970 Potts et al 431/27 3,561,900 2/1971 Walbridge,...43l/256 [75 1 Invent sm'ley Budhn" Fulmn' 3,589,848 6/1971 Potts..43l/78 [73] Assignee: General Electric Company 3,596,133 7/1971 Warrenet al... ..3l7/79 X Filed: J 1971 3,632,285 l/l972 Foster ..43l/264 [21]Appl. No.: 154,429 Primary Examiner-Volodymyr Y. Mayewsky Att0rneyJohnM. Stoudt et al.

[52] US. Cl. ..317/96, 315/206, 431/24,

431/78, 431/264 [57] ABSTRACT [51] Int. Cl ..F23g 3/00 A b n r i nitionsystem for connection to a source of Fleld of Search alternating currentelectric energy. The system has a 315/206 spark generator, including anignition transformer. The primary of ignition transformer is connectedto a 1 References Clted controlled rectifier. The trigger circuit forthe con- UNITED STATES PATENTS trolled rectifier includes a seriesarrangement of a rect1fier, a capaeltance and a voltage breakdown3,393,039 7/1968 Eldridge, Jr. et a1. ..-'.3l7/96 X device. 3,457,4567/1969 Dietz 3,488,131 1/1970 Myers et al ..43 1/24 8 Claims, 1 DrawingFigure I! 54 II o e i PATENTEDJMI 9 ms 3.710.192

I I L L INVENTOR. Sta nley \IBudLane,

ATTO E7.

BURNER IGNITION SYSTEM BACKGROUND OF THE INVENTION This inventionrelates generally to burner ignition systems and, more particularly, tosuch systems for use with gas fueled burners such as domestic furnaces,for instance.

Automatic control systems for burners, such as domestic gas furnaces forinstance, normally provide means for automatic ignition of the gas. Fora number of years the most common approach was the use of a standingpilot. In such igniters, a small pilot flame burned continuously and wasused to ignite the gas mixture at the main burner when heat was calledfor. Such systems have a number of drawbacks including the possibilityof the pilot flame being accidentally extinguished.

Over the last several years there has developed the practice of usingspark or arc igniters in such control systems. Spark igniters createsparks or an electric arc to ignite the gas mixture. Many spark ignitersare of the continuous duty type; that is, they repeatedly provide a fullpower charge or are so long as heat is being called for. Such a mannerof operation results in undue wear of the igniter. Many spark igniterswill continue to attempt to light the gas mixture indefinitely in theevent heat is called for and the gas mixture does not ignite. This alsocan cause excessive wear. Some controls include expensive andcomplicated additional components to stop operation in the event the gasmixture is not ignited. Also prior art ignition systems provide a sparkor are of only one energy level. Thus, they must be designed to providesufficient energy to ignite the gas mixture even under border line oradverse conditions. Thus, such ignition systems always operate toprovide an arc of greater energy than is really needed in mostinstances. This also leads to excessive wear.

SUMMARY OF THE INVENTION Accordingly, it is a general object of thepresent invention to provide an improved burner ignition system.

Another, more specific, object is to provide an improved ignition systemof the electric arc type.

Still another-object is to provide such an improved ignition system inwhich unnecessary arcing is effectively minimized.

Yet another object is to provide such an improved system in which theenergy levels of the arcs produced are minimized.

A further object of the present invention is to provide such an improvedignition system which automatically terminates operation after apredetermined period of time.

In carrying out the invention, in one form, I providea burner ignitionsystem including spark generating means and a controlled rectifieradapted to operatively connect the spark generating means to a supply ofalternating current electric energy. The controlled rectifier has a gatefor application of a control signal to cause conduction of thecontrolled rectifier during half cycles of applied electric energy of afirst polarity. A trigger circuit, including a series arrangement of arectifier, a capacitance and a voltage breakdown device, connects thegate to the supply of alternating current electric energy to causeconduction of the controlled rectifier during predetermined half cyclesof electric energy.

The above mentioned and other features and objects of this invention, aswell as the manner of attaining them will become more apparent, and theinvention itself will be better understood by reference to the followingdescription taken in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING The single FIGURE of the drawing is aschematic electric circuit diagram of an improved burner ignition systemin accordance with one form of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawingthere is shown in somewhat schematic form a burner ignition systemdesigned to provide a timed ignition trail for a fuel burner. Uponsuccessful ignition, the system will maintain the fuel valve in an opencondition until power is removed from the circuit. At the same time thesystem automatically will cease the ignition trail and close the gasvalve in the event ignition does not occur within the timed period.

The system includes a pair of supply conductors 11 and 12 for connectingthe ignition system to a suitable source of alternating current electricenergy, such as a volt household circuit in the case of a domestic gasfurnace application for instance. For purposes of illustration conductor11 may be considered to be a power conductor and conductor 12 the groundconductor, as indicated by the ground symbol 13. From conductor 11 toconductor 12 a branch circuit extends through a rectifier or diode 14, acontrol coil 15 for the gas valve and a controlled rectifier 16 to aconductor 17 which leads to the ground conductor 12. A filter capacitor18 is connected across the control coil 15 so that the control coil willoperate properly on half wave electrical energy. The controlledrectifier 16 includes an anode 16a, a cathode 16c and a gate 16g.

Another branch circuit extends from the conductor 11 through a rectifieror diode 19, resistor 20, capacitor 21 and the primary 22 of a pulse orignition transformer 23 to the conductor 17. The pulse transformer 23also includes a secondary 24 with the secondary having a substantiallygreater number of turns than the primary so that a pulse in the primarywinding will cause pulse of higher voltage in the secondary winding. Afree wheeling or circulating diode or rectifier 25 is connected acrossthe primary 22 of the transformer. A conductor 26 connects the junctionbetween resistance 20 and capacitor 21 and the junction between thecontrol coil 15 and the anode 16a of the controlled rectifier 16.

A trigger circuit including a series arrangement of a capacitor 27, adiode or rectifier 28 and a voltage breakdown deice in the form of neontube 29 is connected between the anode 16a and the gate 16g of thecontrolled rectifier 16. A resistor 30 is connected between the gate ofthe controlled rectifier 16 and the conductor 17 so as to effectively beconnected between the gate 16g and the cathode 16c of the controlledrectifier. A discharge circuit for the capacitor 27 includes a resistor31 and a switch 32. As indicated by broken line 33, the switch 32 isinterconnected with a switch 34 sothat when switch 32 is open switch 34is closed and when switch 32 is closed switch 34 is open.

Both switches may, for instance, be controlled by a heating thermostat(not shown) so that, when heat is desired, switch 34 is closed andswitch 32 is open; and, when no heat is desired, switch,34 is open andthe switch 32 is closed. L"

The secondary 24 of the pulse transformer is connected between conductor17 anda spark or arc electrode 35 which, in turn, is spaced slightlyfrom the gas burner schematically illustrated at 36. Thus, when a pulseis generated in the secondary 24, an electric are or spark is causedbetween the electrode 35 and the burner 36. Gas is provided to theburner 36 through a supply pipe or conduit 37 from a suitable source(not shown) and the flow of gas may be controlled by valve schematicallyillustrated at 38. It will be understood that the control coil isinterconnected with the valve 38 to control the opening and closing ofthe valve so that the valve is open only when the coil is energized. Itwill be understood that, as is well-known in the art, the control coil15 may be directly connected to the valve 38 or may be the control coilof a relay with the relay being in an additional circuit which controlsthe energization of the valve.

A flame sensor schematically illustrated at 40 is electrically connectedby conductors 41 and 42 to a flame detection circuit schematicallyillustrated by the block 43. The flame detection circuit is providedwith electrical energy by conductors 44 and 45 which are connected tothe supply conductors 11 and 12 respectively. The flame detectioncircuit 43 is connected to the junction between diode 28 and neon tube29 through diode or rectifier 46. The flame sensor 40 and flamedetection circuit 43 may take any one of a number of forms which arewell-known in the art. An electrical signal is provided through thediode 46 in response to the flame sensor sensing flame (such as thatillustrated schematically at 47). By the same token, when the flamesensor does not sense flame no signal is provided by the flame detectioncircuit through the diode 46. it will be understood that the flamesensor may be an ultraviolet detector, a thermocouple or otherwell-known sensor, for instance.

When the control thermostat calls for no heat, switch 34 is opende-energizing the entire circuit and causing the flame at burner 36 tobe extinguished. At the same time switch 32 is closed so as to bleed offany charge which has accumulated on the capacitor 27. When thethermostat subsequently calls for heat, switch 34 is closed and switch32 is opened. The capacitor 21 charges through the diode l9, resistorand diode 25. When the charge on capacitor 21 reaches a level just abovethe firing voltage for the neon tube 29, which may conveniently beapproximately 90 volts, the neon tube fires or conducts and a gatesignal is provided to the controlled rectifier 16, which then goes intoconduction. The anode 16a of the controlled rectifier quickly drops towithin about 1 volt of ground. However, the capacitor 27 has gained asmall incremental charge due to the gate current flowing through it.This charge is clamped or held on capacitor 27 due to the plurality ofthe diode 28.

As the supply voltage passes through zero, that is as the voltage onconductor 11 passes through zero between a condition positive relativeto conductor 12 and a condition negative relative to conductor 12, the

controlled rectifier 16 turns off. When the line voltage again becomespositive, that is the voltage of conductor 11 becomes positive withrespect to conductor 12, the capacitor 21 is recharged so as to againcause conduction of the controlled rectifier. However, this secondcharge on capacitor 21 must reach a value just above the firing voltageof the neon tube 29 plus the incremental charge on capacitor 27 before agate signal will be provided to the gate 16g of the controlledrectifier. When a sufficient charge accumulates on capacitor 21, a gatesignal is again provided to gate 16g through the capacitor 27, diode 28and neon lamp 29 so that the control rectifier 16 again conducts. Thevoltage at the anode 16a of the control rectifier quickly falls towithin about one volt of ground. During this second firing an additionalincremental charge accumulates on the capacitor 27 due to the gatesignal. This action is repeated each positive half cycle until the sumof the voltage on capacitor 27 and the firing voltage of neon tube 29approaches the peak line voltage. When this occurs, no more gate currentis available via the capacitor 27.

Each time the controlled rectifier 16 is gated, current flows throughdiode 14 and control coil 15. The capacitor 18 acts as a half wave d.c.filter and provides current to the coil 15 during negative half cyclesso that the half wave energy provided by controlled rectifier 16 issufficient to hold the valve 38 in an open condition and fuel or gas isprovided to the burner 36.

Also, each time the controlled rectifier 16 is gated, capacitor 21discharges through the control rectifier and the primary 22 of the hightension pulse transformer 23. The high turns ratio between the primary22 and the secondary 24 of the transformer 23 generates a high voltagein the secondary sufficient to cause a spark or arc between theelectrode 35 and the burner 36. This spark or are is designed to causethe gas mixture at the burner to ignite. The diode 25 in addition toserving as a path for charging the capacitor 21 also serves as a freewheeling diode for the transformer primary 22 to allow the field in aprimary to collapse during negative half cycles.

Since the charge on capacitor 21 must build to a higher voltage leveleach succeeding positive half cycle, in order to overcome the firingvoltage of neon tube 29 plus the incremental voltage charge of capacitor27, the voltage generated in the secondary 24 of the transformer at eachfiring is greater than the' previous voltage and each spark or arc is ofa greater energy level than the previous one. Thus, the energy of thearc begins at a low level and increases with each arc to provide an evengreater chance of ignition while keeping wear to a minimum.

Assuming there is some sort of malfunction so that a flame is notproduced, as soon as the incremental charge on capacitor 27 builds to alevel sufficient to prevent further gate signals through that capacitorthe controlled rectifier will cease to be gated. This halts the halfwave current flow through the control coil 15 and the gas valve 38 isde-energized and closes. Also the ignition arcs or sparks will stop ascapacitor 21 no longer is being dumped. This prevents unnecessary weardue to continuous high level arcing over long periods of time andprevents a dangerous situation from developing as a result of continuedunignited gas flow.

Assuming that a flame is established, the flame sensor 40 will sense theflame and provide a control signal through conductors 41 and 42 to theflame detection circuit. The flame detection circuit, which may take anyone of a number of forms, provides a signal every half cycle throughdiode 46. This signal is larger than the breakdown or firing voltage ofthe neon lamp 29 so as to gate the control rectifier 16. This keeps thecontrol coil energized so that the control valve 38 is maintained openedand gas flow continues to the burner. This action of the flame sensorand flame detection circuit does allow repeated partial charging of thecapacitor 21 and then its dumping through the control rectifier l6 andprimary 22 of the high tension transformer 23. However, the gating ofthe control rectifier by the detection circuit may be designed to occurrelatively early in each positive half cycle so that the energyavailable in capacitor 21 and the line voltage at that time isrelatively low and the are provided is ofa relatively low energy level.

Such operation will continue so long as the thermostat calls for heat.When the thermostat calls for no heat, switch 34 is opened to completelyde-energize the circuit. This closes the gas valve 38 and the flame isextinguished. At the same time switch 32 is closed to provide acirculating path for discharging the incremental voltage accumulated oncapacitor 27. Thus, the next time the thermostat calls for heat thecapacitor 27 will begin in a noncharged state and the initial arebetween electrode 35 and burner 36 will be of a relatively low level.

I have found that one suitable circuit in accordance with the schematicdiagram shown may be provided utilizing the following components:

diode l4 General Electric 1N5060 controlled rectifier General ElectricC106B capacitance 18 20 microfarads, 160 volts diode l9 General Electric1N5060 resistance 20 1.3 kilohms, 5 watts capacitance 21 1.0 microfaraddiode 25 General Electric 1N5060 capacitance 27 .22 microfarad diode 28General Electric 1N5060 neon lamp 29 General Electric SAB resistance 30l kilohm, :6 watt resistance 31 15 kilohms, 1% watt diode 46 GeneralElectric 1N5060 with the above indicated components and values theignition trial period provided is approximately 20 seconds.

It should be apparent to those skilled in the art that while I havedescribed what, at present, is considered to be the preferredembodiments of this invention, in accordance with the Patent Statutes,changes may be made in the disclosed system without actually departingfrom the true spirit and scope of this invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

l. A burner ignition system, including:

a. spark generating means;

b. a controlled rectifier adapted to operatively connect said sparkgenerating means to a supply of al ternating current electric energy forproviding spark generating power to said spark generating means uponconduction of said controlled rectifier;

2. A burner ignition system as set forth in claim 1 further includingmeans selectively effective to discharge said capacitance.

3. A burner ignition system as set forth in claim 1 wherein saidcontrolled rectifier includes an anode, a cathode and a gate; saidtrigger circuit being connected between said anode and said gate.

4. A burner ignition system, for connection to a source of alternatingcurrent electric energy, including:

a. an ignition transformer having a primary winding and a secondarywinding; spark generating device connected to said secondary winding;

c. a controlled rectifier adapted to operatively connect said primary ina supply circuit from the source of electric energy for providingelectric energy to said primary winding upon conduction of saidcontrolled rectifier;

d. said controlled rectifier having a gate terminal for application of acontrol signal to said controlled rectifier to cause conduction of saidcontrolled rectifier during half cycles of applied electric ener 8};

e. a trigger circuit for connecting said gate terminal to the source ofelectric energy; and

f. said trigger circuit including a series arrangement of a rectifier,adapted to conduct during half cycles of the same polarity as saidcontrolled rectifier, a capacitance and a voltage breakdown device.

5. A burner ignition system as set forth in claim 1 further includingmeans selectively effective to discharge said capacitance.

6. An ignition system as set forth in claim 4 wherein said controlledrectifier includes an anode, a cathode and a gate; said trigger circuitbeing connected between said anode and said gate.

7. A burner ignition system for connection to a 50 source of alternatingcurrent electric energy, including:

a. an ignition transformer having a primary winding and a secondarywinding;

a spark generating device connected to said secondary winding;

c. a controlled rectifier having an anode, a cathode and a gate;

. first circuit means connecting said anode and cathode across thesource of alternating current electric energy;

e. a storage capacitance; second circuit means connecting said storagecapacitance across the source of alternating current electric energywhen said controlled rectifier is nonconductive and connecting saidstorage capacitance in series with said primary of said ignitiontransformer through the anode-cathode path of said controlled rectifierwhen said controlled rectifier is conductive;

f. a trigger circuit, including a series arrangement of a rectifier, asecond capacitance and a voltage breakdown device, connected betweensaid anode and said gate of said controlled rectifier.

8. A burner ignition system as set forth in claim 7, further includingmeans selectively effective to discharge said capacitance.

1. A burner ignition system, including: a. spark generating means; b. acontrolled rectifier adapted to operatively connect said sparkgenerating means to a supply of alternating current electric energy forproviding spark generating power to said spark generating means uponconduction of said controlled rectifier; c. said controlled rectifierhaving a gate for application of a control signal to said controlledrectifier to cause conduction of said controlled rectifier during halfcycles of applied electric energy of a first polarity; d. a triggercircuit for connecting said gate to a supply of alternating currentelectric energy; and e. said trigger circuit including a seriesarrangement of a rectifier, adapted to conduct during half cycles of thesame polarity as said controlled rectifier, a capacitance and a voltagebreakdown device.
 2. A burner ignition system as set forth in claim 1further including means selectively effective to discharge saidcapacitance.
 3. A burner ignition system as set forth in claim 1 whereinsaid controlled rectifier includes an anode, a cathode and a gate; saidtrigger circuit being connected between said anode and said gate.
 4. Aburner ignition system, for connection to a source of alternatingcurrent electric energy, including: a. an ignition transformer having aprimary winding and a secondary winding; b. spark generating deviceconnected to said secondary winding; c. a controlled rectifier adaptedto operatively connect said primary in a supply circuit from the sourceof electric energy for providing electric energy to said primary windingupon conduction of said controlled rectifier; d. said controlledrectifier having a gate terminal for application of a control signal tosaid controlled rectifier to cause conduction of said controlledrectifier during half cycles of applied electric energy; e. a triggercircuit for connecting said gate terminal to the source of electricenergy; and f. said trigger circuit including a series arrangement of arectifier, adapted to conduct during half cycles of the same polarity assaid controlled rectifier, a capacitance and a voltage breakdown device.5. A burner ignition system as set forth in claim 1 further includingmeans selectively effective to discharge said capacitance.
 6. Anignition system as set forth in claim 4 wherein said controlledrectifier includes an anode, a cathode and a gate; said trigger circuitbeing connected between said anode and said gate.
 7. A burner ignitionsysTem for connection to a source of alternating current electricenergy, including: a. an ignition transformer having a primary windingand a secondary winding; b. a spark generating device connected to saidsecondary winding; c. a controlled rectifier having an anode, a cathodeand a gate; d. first circuit means connecting said anode and cathodeacross the source of alternating current electric energy; e. a storagecapacitance; second circuit means connecting said storage capacitanceacross the source of alternating current electric energy when saidcontrolled rectifier is nonconductive and connecting said storagecapacitance in series with said primary of said ignition transformerthrough the anode-cathode path of said controlled rectifier when saidcontrolled rectifier is conductive; f. a trigger circuit, including aseries arrangement of a rectifier, a second capacitance and a voltagebreakdown device, connected between said anode and said gate of saidcontrolled rectifier.
 8. A burner ignition system as set forth in claim7, further including means selectively effective to discharge saidcapacitance.